The present invention is mainly directed to an occupant classification and weight sensory system.
Vehicle occupant protection systems, which are activated in response to a vehicle crash for those people of mitigating occupant injury, are well known in the art. A vehicle may contain automatic safety restraint actuators such as front and side air bags, seat belt pretensioners, and deployable knee bolsters. The occupant protection system may further include a collision/crash sensor for sensing the occurrence of a vehicle crash and for providing an electrical signal indicative of the crash severity.
Several known occupant protection systems include an occupant classification or weight detection system. The occupant classification/weight detection system could consist of occupant weight or size determination based on force/load sensors, capacitive/electric sensors, resistive load distribution sensors, ultrasonic sensors, infrared sensors, and/or image based sensors. A controller, which is connected to one or a combination of these sensors, controls the inflatable protection module in accordance to the sensed size or weight of the occupant. In response to the sensed occupant weight or size, one or more deployment aspects of the restraint system, such as the air bag, may be adjusted. A protection system with adjustable aspects of deployment is commonly referred to as an “adaptive” protection system. Specifically, if the occupant is so small or light that deploying the air bag will not enhance protection of the occupant, it may be desirable to suppress the activation of the occupant protection module. In such a case, air bag deployment may even be more detrimental than no deployment at all.
Occupant classification and weight estimation are key components of adaptive occupant protection systems. There are several types of such systems but many of them suffer from serious shortcomings. A system that classifies an occupant based on the strength of an electric field (or the capacitance of the human body) may be misled if a minimum contact surface area between the occupant and the sensor is not reached, for instance. A system that classifies the occupant based on the load distribution, size, shape and/or orientation of the occupant's posteriors may not be reliable as people come in varying heights, weights and body shapes and sizes. A system that relies solely on force/load sensors cannot account for false readings due to external forces such as accelerations or information loss due to body angle or foot position. Different obstacles such as a map, a book, a newspaper, or a mirror, for instance, could occlude signals from ultrasonic and video based systems. Also, a lighter or a cigarette could blind an infrared-based system.
This invention is based on a simple fact—in an occupant classification or weight detection system, false readings due to external forces and losses of information due to body angle and foot position can be compensated for, if these factors can be detected and measured reliably and consistently. This invention provides a simple yet reliable method to compensate for these factors to accurately classify an occupant and determine the occupant's weight.